linux-kernel - Re: [PATCH] x86, selftests: Add a test for the "sysret_ss

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Message-ID: <553B9CCD.4040408@redhat.com>
Date:	Sat, 25 Apr 2015 15:55:25 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>
CC:	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Brian Gerst <brgerst@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86, selftests: Add a test for the "sysret_ss_attrs"
 bug

On 04/25/2015 12:09 AM, Andy Lutomirski wrote:
> On AMD CPUs, SYSRET can return with a valid SS descriptor with with
> the hidden attributes set to an unusable state.  Make sure the kernel
> doesn't let this happen.  This detects an as-yet-unfixed regression.
> 
> Note that the 64-bit version of this test fails on AMD CPUs on all
> kernel versions, although the issue in the 64-bit case is much less
> severe than in the 32-bit case.

Confirmed to detect the "bug" in 64-bit userspace.

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